1. Technical Field
The invention relates to a power converting apparatus, and more particularly, to a buck-type and a buck-boost type power converting apparatus.
2. Related Art
Along with the progress of electronic technology, electronic products have become indispensable in our daily lives. In order for the electronic products to provide diverse functions, it has become the inevitable trend to supply a variety of electric powers for a plurality of application circuits to be utilized in the electronic products. While the most common method is, the required electronic power generated through a so-called voltage converter.
In general, most voltage converters require a pulse width modulation signal generating circuit to provide a pulse width modulation signal to drive a power transistor in the voltage converter, thereby executing the action of voltage converting. Under the consideration of green power, the conventional technique is usually employed the output voltage generated by the voltage converter to carry out the process, so as to be an auxiliary operating power of the pulse width modulation signal generating circuit. It should be noted that, while the voltage of the output voltage generated by the voltage converter and the voltage of the operating power of the pulse width modulation signal generating circuit have a certain difference, the action for generating the aforementioned auxiliary operating power requires more complicated circuit elements to implement, such that the cost of circuits is raised. Furthermore, there are also some technique difficulties on providing a stable operating power for the pulse width modulation signal generating circuit according to the output voltage generated by the voltage converter, which is also becoming an important topic for the designer in the field.